Method for mounting a drive shaft of a compressor

ABSTRACT

The invention concerns a method for mounting a drive shaft ( 19 ) of a compressor, particularly a hermetical refrigerant compressor, which has a motor with a stator ( 1 ) and a rotor ( 23 ), connected with the drive shaft ( 19 ) and located in a rotor opening ( 4 ) of the stator ( 1 ), a first bearing support ( 8 ) and a second bearing support ( 29 ) being connected with the stator ( 1 ), a first bearing ( 15 ) for the drive shaft ( 19 ) being mounted in the first bearing support ( 8 ) and a second bearing ( 28 ) for the drive shaft ( 19 ) being mounted in the second bearing support ( 29 ). It is endeavoured to provide a method for mounting a drive shaft, in which the use of components with relatively large manufacturing tolerances will still result in a good alignment of the drive shaft in relation to the stator. For this purpose, at least the first bearing support ( 8 ) is provided with a positioning stop for the first bearing ( 15 ) after mounting the first bearing support ( 8 ) on the stator ( 1 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. Ser. No. 11/135,873entitled ‘Method for Mounting a Drive Shaft of a Compressor’, to FrankHolm Iversen, et al., filed on May 24, 2005, and claims the benefit ofthe filing date thereof under 35 U.S.C. §120. The present invention alsoclaims priority from German Patent Application No. 10 2004 025 678.0,filed on May 26, 2004. The contents of both applications areincorporated by reference herein.

FIELD OF THE INVENTION

The invention concerns a method for mounting a drive shaft of acompressor, particularly a hermetical refrigerant compressor.

BACKGROUND OF THE INVENTION

Refrigerant compressors have become products manufactured in largenumbers, and should therefore be manufactured in the most cost effectivemanner possible. As, however, refrigerant compressors are practicallyoperating all the year round, the energy consumption of the motor, whichis required for driving the compressor unit, must be kept as small aspossible. This again requires that, for example, the rotor and thestator are assembled with the best possible mutual alignment to keep theair gap between rotor and stator small, which reduces energy losses.

U.S. Pat. No. 6,095,768 shows a refrigerant compressor with a cup-shapedstator housing, whose upper end is open. The open end is bridged by acrossover. Self-aligning bearings for the drive shaft are inserted bothin the crosshead and in the bottom of the stator housing. Even thoughthese bearings permit a certain deviation of the drive shaft from theaxis of the stator, a relatively exact alignment of the crosshead mustbe ensured, so that the crosshead is perpendicular to the drive shaft.

Another refrigerant compressor is known from U.S. Pat. No. 3,762,837.Here, the drive shaft is supported on both sides of a crankpinarrangement. The rotor is located on the other side of a bearing. Bothbearings are radially displaceable and after mounting the motor and thecompressor arrangement they have to be individually aligned and fixed toensure a uniform air gap between the rotor and the stator. For thealignment, screws are loosened and the bearings displaced. Then thescrews are tightened again. Thus, the bearings are only held by means ofclamping.

EP 0 524 552 A1 shows a hermetical refrigerant compressor withdouble-supported drive shaft, the upper bearing being fixed in a block.The lower bearing is fixed on the stator by means of a holding element,so that the rotor can align itself in relation to the stator of themotor.

In all cases, relatively accurately manufactured components are requiredto keep the air gap between the rotor and the stator small and to alignthe drive shaft perpendicularly to the bearings. A “leaning” drive shaftwill eventually cause relatively heavy wear on the bearings. Further, aninsufficient alignment causes frictional losses in the bearings, whichagain cause increased energy consumption.

SUMMARY OF THE INVENTION

The invention is based on the task of providing a method for mounting adrive shaft, which ensures a good alignment of the drive shaft to thestator, also when using components with relatively large manufacturingtolerances.

With a method as mentioned in the introduction, this task is solved inthat at least the first bearing support is provided with a positioningstop for the first bearing after mounting the first bearing support onthe stator.

With this method, a uniform air gap between the rotor and the stator isachieved, which can even be heavily reduced. Frictional losses in thebearings are avoided. This also applies, when relatively cheap sheetmetal parts are used for the compressor, that is, parts with relativelylarge manufacturing tolerances. Firstly, the first bearing support ismounted on the stator. This gives the bearing support an unchangeableposition in relation to the rotor opening. Then, the positioning stopfor the first bearing can be manufactured with a fixed dependence on theposition of the rotor opening. Thus, the positioning stop is notmanufactured until after the mounting of the first bearing support, butafter the manufacturing, it is no longer changed in relation to therotor opening. When the first bearing is then aligned on the positioningstop, the first bearing has an exact concentrical alignment in relationto the rotor opening.

Preferably, an edge of an opening is used as positioning stop, said edgebeing manufactured after mounting the bearing support on the stator. Thefirst bearing is then inserted in the opening and is then aligned to beexactly concentrical to the rotor opening. Instead of an opening, alsoan impressing can be used.

Preferably, with a vertically aligned drive shaft, the bearing supportof the upper bearing is fixed on the stator, and then the positioningstop is formed. In most refrigeration compressors the motor is made witha vertically oriented drive shaft. The drive shaft then “hangs” on theupper bearing, in whose vicinity usually also the crank pin for drivingthe compressor arrangement is located. In this area, an exact alignmentof the drive shaft in the rotor opening is particularly important.

It is also advantageous, when a tool is used for manufacturing thepositioning stop, at least a part of this tool being locatedconcentrically in the rotor opening. The rotor opening itself is usedfor centring the tool for the manufacturing of the positioning stop.Thus, it is ensured that the positioning stop has exactly the desiredalignment to the rotor opening.

It is particularly preferred that the part fills the cross-section ofthe rotor opening. Thus, the rotor opening or at least an axial sectionof it is filled with the tool, so that the tool is practically no longerradially displaceable in the rotor opening. When, then the positioningstop is formed, the positioning stop is aligned concentrically to therotor opening with a high accuracy.

Preferably, a punch is used as tool. With a punch, for example, anopening can be punched, whose edge then serves as positioning stop.

Preferably, a bearing support is used, whose opening has short measurein relation to the bearing, the opening being extended to the measure ofthe bearing. When using a punch, this has the advantage that afterfixing the bearing support only a fine punch step is required to bringthe opening to the final measure. This further simplifies themanufacturing process, as only little material has to be removed, whichmeans that the forces required to manufacture the final opening aresmaller.

Alternatively or additionally, it is ensured that a calotte bearing isused as bearing, an area surrounding the opening being shaped to abearing shell by means of an impressing step. Also in this case, the“local” manufacturing ensures that the centre of the bearing shell liesexactly on the axis of the stator.

Preferably, the second bearing is mounted on the second bearing support,aligned centrically to the rotor opening by means of an auxiliary tool,which is fixed at at least two alignment positions on the stator, thesecond bearing support then being fixed on the stator. Thus, anovercorrection is avoided.

It is preferred that holes in the metal sheets of the stator are used asalignment positions, said holes being made together with the rotoropening. The stator is usually made of stacked metal sheets, in whichthe rotor opening is made in that all the metal sheets are provided witha punching. When making this punching, holes can be punched at the sametime for later use as fixing for the auxiliary tool. These holes arethen positioned in relation to the rotor opening with a very highaccuracy.

It is also advantageous that the second bearing is aligned aftermounting on the drive shaft. In this case, it is ensured that the axisof the drive shaft corresponds exactly to the axis of the stator.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention is described on the basis of a preferredembodiment in connection with the drawings, showing:

FIG. 1 is a schematic cross-section through a stator;

FIG. 2 is a perspective view of the stator;

FIG. 3 is a sectional view according to FIG. 1 with inserted tool;

FIG. 4 is a perspective view according to FIG. 2 after forming anopening for the first bearing;

FIG. 5 is a sectional view of the stator with inserted upper bearing;

FIG. 6 is a sectional view of the stator with inserted drive shaft;

FIG. 7 is a sectional view with inserted rotor; and

FIG. 8 is a sectional view with inserted lower bearing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a stator 1 of a motor, which is used for driving acompressor, particularly a refrigerant compressor. The stator 1 has asheet pack 2 and a coil, of which coil ends 3 are shown. The sheet pack2 surrounds a rotor opening 4. The rotor opening 4 is made in thatalready during the punching; the sheets forming the sheet pack 2 areprovided with a central opening, so that the rotor opening 4 occurs,when the sheets of the sheet pack 2 are stacked.

A compressor block 5 is mounted and fixedly connected, for example bywelding, on the outside of the sheet pack 2. The compressor block 5 can,for example, be a sheet metal part. The compressor block 5 has a basicunit 7 extending substantially parallel to the axis 6 of the stator 1,on which unit 7 a first bearing support 8 is fixed, for example bywelding. After fixing on the basic unit 7, the first bearing support 8forms a one-side suspended beam, which extends across the rotor opening4. Both the basic unit 7 and the first bearing support 8 can be made ina cost-effective manner from punched and shaped sheet metal parts. Abovethe first bearing support 8, the basic unit 7 has a mounting opening 9,which will eventually serve the accommodation of the compressor unititself.

In the section of the first bearing support 8, which could also becalled “upper bearing support”, crossing the rotor opening 4, an opening10 is made for a first bearing, which is intended for supporting thedrive shaft. For this purpose, a lower support part 11 of a punchingdevice, for example an expansion mandrel, is inserted in the statoropening 4. The lower support part 11 fills the stator opening 4, and isno longer movable in the radial direction. The lower support part 11 isengaged against the lower side of the first bearing support 8. An uppersupport part 12 of the punching device is mounted on the first bearingsupport 8 from the upper side, before a punching tool 13 punches theopening 10 in the first bearing support 8. This opening 10 is thusexactly concentrical to the axis 6 of the stator opening 4, no matter ifthe first bearing support 8 has been mounted exactly enough on the basicunit 7 of the compressor block 5 and thus on the stator 1 or not. Theexact alignment of the opening 10 in relation to the rotor opening 4will not be changed during the following mounting steps, as thecompressor block 5 remains fixedly mounted on the stator 1.

The opening 10 in the first bearing support 8 can also be“pre-manufactured” with a predetermined short measure. The first bearingwill not yet fit into this pre-manufactured opening 10. However, theopening can be extended to its final measure by means of a fine punchingstep. This further simplifies the production process, as only littlematerial has to be removed and the required forces are smaller.

When a calotte bearing is used as first bearing (not shown), the area ofthe first bearing support 8 surrounding the first opening 10 can beshaped by means of an impressing step in such a manner that a bearingshell 14 for the calotte bearing appears. Also in this case, the processshown ensures that the centre of the bearing shells is placed exactly onthe axis 6 of the stator 1.

FIG. 5 now shows that a bearing bush 15 is inserted in the opening 10.The bearing bush 15 can be made of sintered metal and has acircumferential, radially projecting flange 16, which bears on the firstbearing support 8 from the upside. The bearing bush 15 is pressed intothe first bearing support 8, a control device 17, which is guided in thelower support part 11, fixing the radial and axial position of the bush15. The force required for pressing in can be supplied by the uppersupport part 12 of the punch. Instead of the upper support part 12, alsoa corresponding pressing tool can be used. During pressing, the uppersupport part 12 is guided on the control device 17, or rather aprojection 18 penetrating the opening 10, so that here radial forcescannot occur either, which could lead to a displacement of the bearingbush 15.

FIG. 6 shows that a drive shaft 19 is inserted in the bearing bush 15.The drive shaft 19 now has an axis, which is congruent with the axis 6of the stator 1. Under the effect of the gravity it initially hangsvertically downwards. At the upper end, the drive shaft 19 has a carrierdisc 20, on which a crankpin 21 and a balancing weight 22 are fixed. Thecarrier disc 20 bears on the flange 16 of the bearing bush 15, so thathere the bearing bush 15 does not only form a radial bearing, but alsoan axial bearing. The drive shaft 19 can simply be inserted in thebearing bush 15 from the top.

From FIG. 7 it appears that in a further mounting step a rotor 23 ispressed onto the drive shaft 19, whereas a hold-on (not shown in detail)at the crank-side upper end of the drive shaft 19 adopts the pressingforces. To simplify the pressing process, the rotor 23 can be heated upbefore mounting. After cooling off, it shrinks onto the shaft.

FIG. 8 shows the last step of the mounting. An auxiliary tool 24 withpins 25 is inserted in the positioning openings 26 (FIGS. 2 and 4),which are formed in the sheets of the sheet pack 2. These positioningopenings 26 are manufactured in the same punching process, in which alsothe cut-outs are punched, which will form the rotor opening 4. Thus, thepositioning openings 26 have a very accurated spatial relation to therotor opening 4.

The auxiliary tool 24 has a central opening 27, into which the top ofthe drive shaft 19 is inserted. Before applying the auxiliary tool 24,however, a second bearing 28, which is inserted in a second bearingsupport 29, is pushed onto the drive shaft 19. When, through the bearingbush 15 forming the first bearing, the drive shaft 19, and the auxiliarytool 24, have been positioned accurately in relation to the sheet pack 2of the stator 1, the second bearing support 29 is fixed, for example bywelding, on a leg 30 projecting from the basic unit 7. However, thesecond bearing support 29 can also be fixed on the leg 30 by screwing orriveting.

For the second bearing 28, a calotte bearing is preferred, to balancepossible angle errors between the bearing support 29 and the drive shaft19, if the second bearing support 29 does not extend exactly at rightangles to the drive shaft 19.

After fixing the second bearing support 29 on the basic unit 7, it isthus ensured that the centres of the bearing bush 15 and the second, orlower, bearing 28 as well as the longitudinal axes of the two bearingslie exactly in the longitudinal axis 6 of the stator.

All mounting steps shown can to a large extent be automated. Also whenusing formed sheet metal parts, a high-precision alignment of the rotor23 in relation to the stator 1 can thus be realised. This permits thereduction of the air gap between the rotor 23 and the stator sheet pack2, which will also later give a cost-effective mode of operation.

While the present invention has been illustrated and described withrespect to a particular embodiment thereof, it should be appreciated bythose of ordinary skill in the art that various modifications to thisinvention may be made without departing from the spirit and scope of thepresent invention.

1-11. (canceled)
 12. A tool for mounting a drive shaft bearing to astator, the tool comprising: a first support part having a first supportpart diameter and a first support part surface, the first support partdiameter substantially corresponding to a diameter of a rotor opening ofthe stator, and the first support part surface including a first openingextending into the first support part; and a second support part havinga second support part surface opposing the first support part surface,the second support part surface including a second opening extendinginto the second support part and opposing the first opening; wherein thefirst support part is incapable of radial movement when at leastpartially inserted into the rotor opening.
 13. The tool of claim 12,wherein the first opening is positioned in the first support partsurface so as to substantially correspond to a desired position of thedrive shaft bearing relative to the rotor opening.
 14. The tool of claim12, wherein the first and second support part surfaces are adapted toselectively engage opposing sides of a bearing support positioned acrossthe rotor opening.
 15. The tool of claim 12, wherein the first openinghas an inner cross-sectional profile substantially corresponding to anouter cross-sectional profile of the drive shaft bearing.
 16. The toolof claim 12, further comprising a punching device disposed in the secondopening and displaceable so as to at least partially extend into thefirst opening during a punching operation.
 17. The tool of claim 12,further comprising a control device disposed in the first opening anddisplaceable so as to at least partially extend into the second openingwhile inserting the drive shaft bearing into a bearing support.
 18. Thetool of claim 17, wherein the control device includes a projection, theprojection being the portion of the control device extending at leastpartially into the second opening while inserting the drive shaftbearing into the bearing support, the first opening having an innercross-sectional profile and the projection having an outercross-sectional profile substantially corresponding, respectively, to anouter and an inner cross-sectional profile of the drive shaft bearing soas to inhibit radial displacement of the drive shaft bearing whileinserting the drive shaft bearing into the bearing support.
 19. Acompressor motor comprising: a drive shaft; a stator having a firststator end and a second stator end and a rotor opening extendingtherebetween, the rotor opening surrounding at least a portion of thedrive shaft; a rotor mounted on the drive shaft located in the rotoropening; a first bearing support mounted to the stator first end andhaving a first positioning stop formed therein; and a first bearinglocated with the first positioning stop and rotatably supporting thedrive shaft in the vicinity of the first stator end; wherein the firstpositioning stop is formed in the first bearing support after the firstbearing support is mounted to the stator first end.
 20. The compressormotor of claim 19, further comprising: a second bearing support mountedto the stator second end and having a second positioning stop formedtherein; and a second bearing located within the second positioning stopand rotatably supporting the drive shaft in the vicinity of the secondstator end; wherein the second bearing is located within the secondpositoning stop and aligned concentrically to the rotor opening beforethe second bearing stop is mounted to the stator second end.